EG4 FlexBOSS18
For grid-tied homes that want net metering and whole-home backup at a lower price than the FlexBOSS21. Choose the 21 if you need more battery-only output or a third tracker.
Signature Solar $3,199.99$3,199.99
4.3/5
For grid-tied homes that want whole-house backup and grid sell from one proven inverter. Compare against the FlexBOSS21 first, which costs less for more power.
- 12 kWOutput
- 48 VBattery
- 18,000 WSolar input
- 70 WIdle draw
- 10 yearsWarranty
Check price at Signature Solar$3,999.99Check price at Shop Solar Kits$3,999.99
Price checked October 23, 2026. As an Amazon Associate we earn from qualifying purchases.
Pros
- 12 kW continuous plus net metering covers most whole-home backup jobs
- Three trackers take 18,000 W of panels on roofs facing different ways
- 200 A grid passthrough and a separate generator port
- Ten-year warranty
Cons
- About 70 W idle draw is high for overnight battery use
- Over 120 lb, so it needs a strong wall and two installers
- Costs more than the FlexBOSS21, which has more output
The EG4 kPV family
Every EG4 kPV model we rank, smallest first. Ratings compare each against its own output.
| Model | Output | Rating | Price |
|---|---|---|---|
| EG4 12kPV | 8 kW | 4.2/5 | $2,999.99 |
| EG4 18kPV (this one) | 12 kW | 4.3/5 | $3,999.99 |
How it scores
The rating comes from 5 measured or published factors, each scored 0-100 against fixed reference points for its output. How we rank explains each one.
Specifications
| Model number | 18KPV-12LV |
|---|---|
| Output | |
| Output voltage | 120/240 V split-phase |
| Continuous output | 12,000 W |
| Surge | 15,500 W |
| Peak efficiency | 94% |
| CEC efficiency | 96.9% |
| Idle draw | 70 W |
| Transfer time | 20 ms |
| Parallel units | Up to 10 units |
| Solar | |
| Max PV power | 18,000 W |
| Max PV voltage (Voc) | 600 V |
| MPPT range | 140 to 500 V |
| MPPT trackers | 3 |
| PV current per tracker | 25 A |
| Runs without battery | Yes |
| Battery and grid | |
| Battery voltage | 48 V |
| Battery types | Lithium, lead-acid |
| Max charge current | 250 A |
| Battery communication | Yes |
| Grid sell-back | Yes |
| Generator input | Yes |
| UL 1741 | UL 1741 SB |
| Build | |
| App monitoring | Included |
| Enclosure | NEMA 4X |
| Dimensions | 34.3 x 20.5 x 11.2 in |
| Weight | 121 lb |
| Warranty | 10 years |
| Released | 2023-05 |
Alternatives in this output
Fortress Power Envy Duo 21
For homes with a large roof array that want whole-house backup and grid export from one outdoor unit. It takes more solar than the Envy True 12 for the same price.
Wind & Sun $4,898$4,898
Fortress Power Envy True 12
For grid-tied or off-grid homes that want one outdoor inverter to back up the whole house and export to the grid, with US-based support.
Current Connected $4,898 Wind & Sun $4,898$4,898
Compare
Compare the EG4 18kPV with any other hybrid solar inverter →
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